Process of manufacturing tubular parts



April 14, 1931. R. SCHROEDER 1,800,360

PROCESS OF MANUFACTURING TUBULAR PARTS 7 Original Filed Feb. 25, 1927 mandrel Inventor: K n @wm mama A r. 14, 1931 rsooeea UNITED-STATES 5 PATENT ,omcr

. moan-mi scmwnnna. or 3mm, emamr r or min-screams roam rears Orlhll application fled Iehrnary 85, 1887, Burial na l-10,021, and in Germany larch I, 1926. Divided I and this application filed January 19, 1928. Serial No. 888,749,

thicknesses of the web, and divide the cylinder while on the mandrel or after the My invention relates to a recess of manufacturing tubular parts suc as described 1n my apphcation Ser. No. 170,931 filed February 25, 1927 of which this is a division, in

g which the tubular part is formed by winding a web on a mandrel, an intermediatelayer being inserted between the mandrel and the tube for the purpose of utilizing a single mandrel for various sizes of tubes, the cleara once between theinner diameter of the tube and the outer diameter of the mandrel being made up by the intermediate layer.

It is an object of my invention to improve this process and to this end, instead of the u usual undivided layer, I provide a long1tud1-' nally divided layer wh1ch is more readily withdrawn from the finished tube than an undivided layer.

My invention removes the drawback ingo herent in undivided intermediate layers that they are difiicult to remove from the finished tube and, on being removed, are damaged to an extent which renders them unsuitable for further use. On the other hand by dividing as the intermediate layer according to my invention, I endow it with the resiliency required., for readily removing it from the finished tube without damage to the layer or to the tube.

In reducingmy invention to practice I provide a single layer of suitable web material which is divided in a radial plane or in a plane extending at 'an angle to its radius. It is very important that the joint at the line of division should be absolutely tight as otherwise a ridge will form on the inside of the tubes.

- Instead of a single layer I may any .number of su rimposed layers. erably the lines a on which the la ersaredivided, are 'staggere in the severa layers. Any suitable material may be used for the provide layers according to my invention for instance sheet metal or vulcanized fibre, but

I prefer to make them of fibrous web mate- '.rial which is impre ated with a suitable sizing, for instance ma forma tubular cylinder by winding a we or webs of impregnated paper or fabric on a suitable i mandrel and connecting'the superimposed Pref equal to the required mandrel has been extracted.

For impregnatin the webs, I may use any suitable SlZlD or instance a natural or artificial resin. uch resin ma cial resin ada ted to be hardene and preferabl a con ensation roduct of henol or its erivatives, and ormaldehy e or its polymers as bakelite; insuch case I prefer to bake the cylinder until the artificial resin has-attained the desired degree of hardness.

For instance, in order to construct a la' er, a web of paper impregnated with a con ensation product of phenol and formaldehyde is wound around the mandrel under pressure exerted b a heated roller to form a laminated cyhnder, the thicknesses of the web being connected by the artificial resin. The cylinder is then placed in an oven while still on the mandrel and is baked until the condensation sired degree 0 hardness, and then the baked cylinder is longitudinally divided.

My invention involves the important advantage that a comparatively small stock of mandrels is required which is a great savin as such mandrels must be machined wit great exactness and are therefore expensive, particularly when large mandrels are required. T e waste of material is also greatly reduced because the intermediate ayers may be used over and over a ain. For instance, the diameters of the man rels in stock may var within the limits of to 1% in. and t e clearance between the outer diameter of a given mandrel and the inner diameter of the tubes to be made on the mandrel is made up by intermediate layers which may be to in. thick, such intermediate layers being superimposed with their lines of division sta gered, until the outer diameter of the mandrel lus the total thickness of the intermediate ayers is inner diameter of the roduct has attained the de-' tube. The tube, which may be an insulating c linder for electrical equipment or mac cry, for instance transformers and may Y be made of any suitable materia, such as paper impregnated with artificlal resin adapted to be hardened, particularly a condensation product of phenol and formaldehyde, for instance bakelite, is wound about the intermediate layer under pressure exerted by a heated roller, if desired. The finished tubes or cylinders are then placed m an oven, while still on the mandrel, and

are baked until the bakelite has attained the required degree of hardness, and finally the mandrel an the layer or layers are extracted in succession. As soon as the mandrel has been extracted pressure 1s no longer exerted on the layer or layers so that they mediate layers, one superimposed on the other. a

Fig. 3 shows, on a smaller scale, a mandrel having placed thereon three intermediate layers, surrounded by a web, portions of the layers and the web being shown removed for the sake of showing the arrangement.

The mandrel, which may be made of cast iron, is indicated at 1. At 2, 2 and 2 are shown the intermediate cylindrical layers in superposed. relation. As shown, at 3, 3 and 3 each of these layers is provided with a slit extending parallel to the axis of the cylinder. As clearly shown in Figs. 1 and 2, the edges of sald slits are closely abutting each other, and when several intermediate layers are used, the said slits as shown in Figs. 2'and 3, are in offset or staggered relation.

The mandrel is mounted on a shaft 4 journalled in bearings 5 and carrying a pulley 6 whereby the mandrel can be rotated in the direction of the arrow shown in Fig. 3.

After the intermediate layers have been placed on the mandrel, a web 7 of paper lmpregnated with artificial resin, or other suitable material, is wound around the said layers, the said web forminga cylinder 8. The web being tightly wound around the intermediate layers presses the same against the mandrel so that they will rotate ,therewith and at the same time, the edges of the slits 3, 3 and 3 are so closely pressed against each other that no rib will be formed on the cylinder 8.

After the latter has reached the desired 3 thickness, the shaft 4 is pulled out, and the neoaaee reached the desired degreed of hardness.

Thereupon, first the mandrel 1 and then the intermediate layer or layers are pulled out.

It is, understood that I am not limited to the manufacture ofv cylindrical tubes or cylindrical mandrels, but that my process may be ap lied tothe manufacture of tubes and 0t er hollow arts of any crosssection (square,'rectang ar, elliptical, etc.)

without departing from my invention.

I wish it to be understood that I do not desire to be limited to the exact detailsof construction shown and described since obvious modifications will occur to 'a person skilled in the art. I

In the claims aflixed to this specification no selection of any particular modification of the invention is intended to the exclusion of other modifications thereof, and'the ri ht tosubsequently make claim to any modi cation not covered by these claims isexpresslyy reserved.

I claim: '1. The process of manufacturing tubular parts by winding a web of any suitable material around a mandrel and inserting an intermediate layer between said mandrel and said material, comprisin the step of employing a longitudinally 'vided interme iate layer, with its dividing edges closely abutting 2. The process of manufacturing tubular parts by winding a web of any suitable material around a mandrel and inserting an intermediate layer betweensaid mandrel and said material, comprising the step of employing a plurality of Ion itudinall divided intermediate layers with t eir divi g edges closely abutting.

3. The process of manufacturing tubular parts by' winding a web of any suitable material around a mandrel and inserting an intermediate layer between said mandrel and said material, comprising the steps of employing a plurality of longitudinally divided intermediate layers with their dividing edges closely abutting and arranging said layers with their dividing 'edges in staggered relation. 7

4. The process of manufacturing tubular parts by winding a web of any suitable material around a mandrel and inserting an intermediate layer between said mandrel and said material, comprising the steps of employing a longitudinally divided intermediate layer with its dividing edges closely abutting, and successively extracting said mandrel and said layer from the finished art. P 5-. The process .of manufacturing tubular parts by winding a web of any suitable material around a mandrel, connecting the su erimposed thicknesses of the web into 9. cy inder, dividing -said cylinder, winding a web on said divided cylinder, connecting the thicknesses of said est-mentioned we into an outer tube or cylinder, and extractin from said cylinder said mandrel and sald first-mentioned cylinder in succession.

In testimony whereof, I afiix my signa- 'ture.

' RICHARD SCHBOEDER. 

